Cats could be wildlife destroying machine In the journal Nature Communications. They found that free-ranging cats killed between 1.4–3.7 billion birds and 6.9–20.7 billion mammals annually in the United States. That research has been widely publicized by birders, and widely ignored by everyone else. SOME Researchers suggest that cats kill the majority of birds. A simple way to save the local fauna is to keep your cat at home, or on a leash. Sudan shouldn't let its c